December 2002

Neutrinos and Beyond: New Windows on Nature – Summary

BOARD ON PHYSICS AND ASTRONOMY

Background. Neutrinos are fast moving elusive particles having a mass much smaller than that of an electron. They can arise from a variety of astrophysical objects and events—e.g., the interior of stars and stellar explosions, from cosmic ray interactions with the Earth’s atmosphere, and from particle accelerators. Neutrinos have enormous penetrating power allowing them to traverse the universe without absorption, making them a valuable and unique tool to explore the universe and its origins.

Because they only weakly interact with matter and have tiny mass, neutrinos are very hard to detect. Massive amounts of material along with a means to shield nearly all background radiation are needed to detect sufficient quantities to measure the properties of the neutrinos and their sources. Two recent proposals for such detectors are IceCube and a deep underground laboratory. As part of the FY03 Budget Request for the National Science Foundation (NSF), the NRC was asked to review the scientific merits of IceCube and other proposed neutrino projects in the context of existing and planned facilities throughout the world. The study, carried out by the Neutrino Facilities Assessment Committee, assessed the science problems that the two proposed facilities could address, and the possible redundancy and complementarity among these and other proposals.

Findings and Recommendations. General. The goal of the IceCube experiment is to elucidate the origins and mechanisms of cosmic accelerators, and to yield insight into their neutrino production processes. The deep underground lab would provide an effective shield against cosmic rays permitting the study of important scientific questions that go well beyond those involving neutrinos alone. Both projects were recently endorsed in the NSF/Department of Energy (DOE) long range plans for nuclear and particle physics.

IceCube. This experiment will consist of a large array of phototubes placed in a cubic kilometer of ice deep below the South Pole. The facility, which is to be an international collaboration, has passed technical review and is ready for construction. IceCube, at the forefront of a new era of science, should be capable of observing neutrinos from known astrophysical point sources and expected diffuse sources . Detection of these neutrinos should reveal much about stellar phenomena such as black holes. The planned IceCube experiment can open a new window on the Universe by detecting very high-energy neutrinos from objects across the Universe. The science is well motivated and exciting, the detection technique is proven, and the experiment appears ready for construction. The latter will require appropriate project management, final technical and design decisions, and assurance of strong collaboration.

A New Deep Underground Lab. Underground research was pioneered 35 years ago in the United States with the detection of neutrinos from the Sun. Development of a new underground facility could restore U.S. leadership in this important research area. Such labs are required to study rare forms of penetrating radiation and rare nuclear processes in a low radiation background environment. Two key attributes for an underground lab are required: it must be able to site experiments as deep as 4500 mwe (meters of water equivalent or about 1450 meters of ordinary rock) with future capability of siting them down to 6000 mwe , and it must be located more than 1000 kilometers from accelerators capable of producing intense beams of neutrinos. The latter would allow the use of such beams to study the properties of neutrinos as they travel over long distances, helping to measure the small but important neutrino masses. Siting the lab in the United States would permit the utilization of its powerful particle accelerators already operating. A lab with sufficient shielding could also be a site for various geophysics and geobiology projects. A deep underground laboratory can house a new generation of experiments that will advance our understanding of the fundamental properties of neutrinos and the forces that govern elementary particles, as well as shedding light on the nature of the dark matter that holds the Universe together. Recent discoveries about neutrinos, new ideas and technologies, and the scientific leadership that exists in the U.S., make the time ripe to build such a unique facility. Other critical decisions that are beyond the scope of this report remain concerning site selection, laboratory scope, management, and on-site infrastructure requirements. Every effort should be made to integrate closely the lab’s development with the intended experimental program. Developing sound experimental proposals will require early access to the lab’s facilities.

Redundancy and Complementarity. The primary scientific programs intended for the two facilities are distinct, and essentially no overlap or redundancy in either these goals or facility capabilities exist. Furthermore, internationally, IceCube is unique in its technology and location and is the most advanced project for high-energy neutrino observation on this scale. The wealth of experimental opportunities available in a deep underground lab guarantees that an additional lab would make a significant contribution to international science. In addition, there are likely to be important scientific, economic, and administrative advantages to a centralized national underground lab.

For further information

Copies of the complete report, Neutrinos and Beyond: New Windows on Nature, can be obtained on the National Academy Press.

The National Science Foundation provided support for this project. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors. Visit the Board on Physics and Astronomy for more information.

NEUTRINO FACILITIES ASSESSMENT COMMITTEE

BARRY C. BARISH, Chair, California Institute of Technology, DANIEL S. AKERIB, Case Western Reserve University, STEVEN R. ELLIOTT, Los Alamos National Laboratory, PATRICK D. GALLAGHER, National Institute of Standards and Technology, ROBERT E. LANOU, JR., Brown University, PETER MÉZÁROS, Pennsylvania State University, HITOSHI MURAYAMA, University of California, Berkeley, ANGELA V. OLINTO, University of Chicago, RENE A. ONG, University of California, Los Angeles, R. G. HAMISH ROBERTSON, University of Washington, NICHOLAS P. SAMIOS, Brookhaven National Laboratory, JOHN P. SCHIFFER, Argonne National Laboratory, FRANK J. SCIULLI, Columbia University, MICHAEL S. TURNER, University of Chicago.

Staff

DONALD C. SHAPERO, Director, JOEL R. PARRIOTT, Study Director, TIMOTHY I. MEYER, Program Associate, PAMELA A, LEWIS, Project Associate, NELSON QUIÑONES, Project Assistant.